The molecular epidemiology of plasmid-based dissemination of OXA-48 during a hospital outbreak. Plasmid-based dissemination of OXA-48

Background. A large OXA-48 outbreak in the Netherlands involved the spread of OXA-48-producing Enterobacteriaceae among at least 118 patients, suggesting horizontal transfer of this resistance gene through one or more plasmids. Elucidating transmission dynamics of resistance plasmids is hampered by the low resolution of classic typing methods. Objectives. To investigate the molecular epidemiology of plasmids carrying OXA-48 carbapenemase using a next-generation sequencing approach. Methods. A total of 68 OXA-48-producing Enterobacteriaceae isolated from the hospital outbreak, as well as 22 non-outbreak related OXA-48-producing Enterobacteriaceae from the Netherlands, Libya and Turkey were selected. Plasmids were sequenced using the Illumina Miseq platform, and read sets were assembled and analysed. Results. blaOXA-48 was embedded in transposon Tn1999.2 and located on a ca. 62 kb IncL/M conjugative plasmid in 14 different species. There were a few SNPs (single nucleotide polymorphisms) between all plasmids. Closely related sequence variants of this plasmid were detected is non-outbreak related isolates from the Netherlands and other countries. Thirty-one of 89 OXA-48-producing isolates also harboured blaCTX-M-15, which was not located on the blaOXA-48-carrying plasmid and sequencing of four plasmids harbouring blaCTX-M-15 revealed extensive heterogeneity. Conclusions. A ca. 62 kb plasmid was responsible for the OXA-48 outbreak in a Dutch hospital. Our findings provide strong evidence for both within-host intra-species and between host dissemination of plasmid-based OXA-48 during a nosocomial outbreak. These findings exemplify the complex epidemiology of CPE.